The present invention is directed to an arrangement for retaining harmful substances contained in water seeping from a waste dumping ground body and includes at least one impervious layer of mineral sealing materials such as clay, and a process for forming an impervious layer.
In waste dumping grounds, particularly dumping grounds for waste of an exceptional nature, it is required that the harmful substances contained in the body of the waste dumping ground not reach the biosphere. Accordingly, the waste dumping ground body is provided with a seal which is as watertight as possible, so that, if possible, harmful substances are prevented from flowing from the waste dumping ground. In the past, this problem was solved by providing impervious layers of mineral sealing materials, usually clay, which form a complete closure for the waste dumping ground body, not only to retain the seepage water contained or formed in the dumping ground, but also to prevent precipitation from penetrating into the waste dumping ground body. From a technical point of view, impervious layers of mineral sealing materials can be considered watertight for short periods of time. Since waste must be deposited in waste dumping grounds permanently, that is, perpetually, protection must be considered in terms of geological time periods, that is, very long time periods rather than short periods. In such time periods, the absolute quantity of seepage water flowing from the waste dumping ground, for example, by diffusion through the dumping ground seal, plays an essential role. The use of combination seals formed of mineral sealing materials and sealing webs of plastics material afford a high level of impermeability for the short periods of time of 30 to 50 years mentioned above, however, since the plastics material foils are formed of organic materials which loses its sealing effect due to alterations of matter after such a period of time has elapsed, a significant problem results.